This chapter helps us understand the difference between living things and non-living things by exploring the unique characteristics of living organisms. The chapter begins with an observation about a snail's shell, which seems non-living but is part of a living creature, prompting a discussion about what makes something alive.

We are surrounded by countless objects. Some are living, and some are non-living.

What Sets The Living Apart From The Non-Living?

Living beings possess certain essential characteristics that differentiate them from non-living things. By observing and comparing, we can identify these properties.

Think about the differences between yourself (a living being) and a car (a non-living thing).

Movement

Most living beings, especially animals, can move from one place to another on their own. Non-living things generally do not move by themselves (a car moves because an engine makes it move or it is pushed, not on its own).

However, movement alone is not sufficient to classify something as living, as cars and other machines can move.

Also, some living things, like plants, do not move from place to place, but they do show other types of movement, such as:

• Opening and closing of flowers.
• Leaves of some plants (like 'touch-me-not') folding when touched.
• Insectivorous plants moving to trap insects (e.g., Drosera's sticky hairs moving inward).
• Climber plants winding around supports.

So, while moving from place to place is characteristic of many animals, movement in response to stimuli or growth is also a characteristic of living things, including plants.

Growth

Living beings increase in size over time. This is called growth.

Think about how you grow taller and cannot wear clothes from a few years ago. Similarly, plants start as small seeds and grow into large plants or trees. Animals also grow from young ones into adults.

Non-living things do not grow on their own (a building gets larger if more material is added, but it doesn't grow internally).

Growth is a key characteristic of living organisms.

Nutrition

Living beings need food (nutrition) to obtain energy, grow, and carry out life processes.

Animals eat food, and plants make their own food through photosynthesis (or obtain nutrients from the soil and air). Food provides the necessary resources for growth and development.

Non-living things do not require food.

Respiration

Living beings need to take in air (or oxygen) and give out gases (like carbon dioxide) as part of a process called respiration.

In animals, this often involves breathing, where air is inhaled and exhaled. You can observe breathing in animals by watching the movement of their abdomen.

Plants also respire, taking in and giving out gases through tiny pores called stomata, mainly found on their leaves.

All living beings respire to get energy from their food.

Non-living things do not respire.

Excretion

Living beings produce waste products in their bodies and need to remove them. This process of removing waste is called excretion.

In animals, examples of waste products removed include sweat and urine.

Plants also excrete, for instance, by releasing excess water and minerals through structures on their leaves.

Non-living things do not excrete.

Response To Stimuli

Living beings can sense changes in their surroundings and react to them. These changes are called stimuli (singular: stimulus), and the reaction is called a response.

Examples of stimuli and responses in animals:

• Stimulus: Stepping on a sharp object. Response: Quickly pulling your foot away.
• Stimulus: Touching a hot object. Response: Quickly withdrawing your hand.

Plants also respond to stimuli:

• Stimulus: Touch (for a 'touch-me-not' plant). Response: Folding of leaves.
• Stimulus: Sunlight. Response: Plants growing towards light.
• Stimulus: Sunset (darkness). Response: Leaves of certain plants folding (e.g., Amla).

The ability to sense and respond to stimuli is a vital characteristic of living things.

Non-living things do not respond to stimuli in this way.

Reproduction

Living beings have the ability to produce new individuals of their own kind. This process is called reproduction.

Animals reproduce by giving birth to young ones (like cats having kittens, dogs having puppies) or by laying eggs (like birds laying eggs from which chicks hatch). Plants reproduce through seeds, spores, or other parts.

Reproduction is essential for the continuity of life for each species.

Non-living things cannot reproduce on their own.

Death

All living beings have a limited lifespan. After living and going through various life stages, living beings eventually die.

When a living being ceases to exhibit the essential characteristics of life (movement, growth, respiration, etc.), despite having the necessary conditions, it is considered dead.

Non-living things do not undergo a life cycle ending in death in the same way.

In summary, the key characteristics of living beings are Movement, Growth, Nutrition, Respiration, Excretion, Response to Stimuli, Reproduction, and eventually Death. The absence of these characteristics helps us identify non-living things.

Based on these characteristics, we can classify objects around us. For instance, a pigeon moves, grows, eats, respires, excretes, responds, reproduces, and eventually dies, making it living. A pencil does none of these, making it non-living.

What about a seed? While a dry seed may not seem to exhibit all characteristics (it doesn't actively move, respire strongly, excrete, or respond visibly), it has the potential for life. Under favorable conditions, it will germinate, grow, respire, etc. Therefore, a seed is considered a living thing in a dormant or inactive state.

Essential Conditions For Germination Of A Seed

For a seed to become a new plant, it needs to start growing, a process called germination.

Required Conditions

Seed germination is dependent on specific environmental conditions.

An experiment with seeds in different conditions (Pot A: no water, sunlight; Pot B: excess water, sunlight; Pot C: moist soil, dark; Pot D: moist soil, sunlight) helps identify these conditions.

Pot with bean seeds	Availability of Air	Availability of Sunlight	Availability of Water	Seed germination Observation	Possible reason for the observation
A: In direct sunlight and without water	Yes	Yes	No	No germination	Lack of water.
B: In direct sunlight and excess water	No (soil waterlogged)	Yes	Excess	No germination (or poor)	Lack of air due to waterlogging.
C: In complete dark and moist soil	Yes	No	Moderate	Germination occurs	Water and air are available; light is not essential for germination.
D: In direct sunlight and moist soil	Yes	Yes	Moderate	Germination occurs	All necessary conditions (air, water) for germination are met.

Based on such observations, the essential conditions for most seeds to germinate are:

• Water
• Air

Sunlight is generally not essential for germination itself, although it is crucial for the seedling's growth *after* germination.

Water

Water softens the seed coat (the outer covering) and allows the tiny plant structure inside, the embryo, to become active and start growing. Water is necessary for the biochemical processes within the seed to begin germination.

Air And Soil

Seeds need air (specifically oxygen) for respiration during germination. This air is usually found in the spaces between soil particles. Soil also provides support and moisture retention.

Light And/Or Dark Conditions

For most seeds, light is not required for germination. In fact, some seeds need darkness to germinate and are covered with soil. However, a few types of seeds require light for germination.

Once the seedling emerges from the soil, sunlight becomes absolutely necessary for photosynthesis, which is how the plant makes its food for further growth.

Considering that a seed, under the right conditions, can grow, respire, respond (to conditions), excrete (during metabolism), and reproduce later in its life cycle, a seed is classified as living.

Growth And Movement In Plants

Plants exhibit growth and movement, often in response to environmental stimuli like sunlight and gravity.

Response To Sunlight

Plants grow towards sources of light. This directional growth response is called phototropism.

Root And Shoot Growth Direction

An experiment with germinated seedlings placed in different orientations and light conditions demonstrates this:

• When a seedling is placed upright in uniform sunlight, the shoot (stem and leaves) grows upwards, and the root grows downwards.
• When a seedling is placed inverted (upside down), the root bends and grows downwards (towards gravity), and the shoot bends and grows upwards (away from gravity and towards light if present).
• When a seedling is placed upright but receives light from only one direction, the shoot bends and grows towards the source of light, while the root continues to grow downwards (influenced by gravity).

Conclusion: Plant shoots grow upwards and exhibit movement towards sunlight (positive phototropism), while plant roots grow downwards (positive gravitropism), regardless of the plant's orientation or direction of light (though light can indirectly affect root growth).

Extra Information: Sir Jagadish Chandra Bose was a pioneering scientist who conducted experiments proving that plants respond to stimuli, using instruments like the crescograph to measure their growth and responses.

Life Cycle Of A Plant

Living beings go through a series of stages from birth to death. This sequence of stages is called a life cycle.

Stages Of Plant Life Cycle

The life cycle of a flowering plant, like a bean plant, involves several stages:

1. Seed: The life cycle begins with a seed.
2. Germination: Under favorable conditions (water, air, suitable temperature, sometimes light/dark), the seed germinates and a seedling emerges.
3. Growth: The seedling grows into a mature plant, developing leaves, stem, and roots.
4. Flowering: The mature plant produces flowers.
5. Fruit/Seed Production: Flowers develop into fruits, which contain new seeds.
6. Death: After producing seeds, the plant eventually completes its life cycle and dies.

The seeds produced continue the cycle by germinating into new plants, ensuring the continuity of the species.

Life Cycle Of Animals

Animals also undergo a life cycle with different stages, often involving significant changes in appearance or habitat.

Life Cycle Of A Mosquito

Mosquitoes are insects that can transmit diseases. Preventing their breeding is important for health.

Mosquitoes reproduce by laying eggs, typically on or near water. Stagnant water provides a breeding ground because it is where their initial life stages live.

The life cycle of a mosquito has four distinct stages:

1. Egg: Female mosquitoes lay eggs.
2. Larva: Eggs hatch into larvae, which live in water. They are worm-like and can be seen in stagnant water. Larvae need to come to the water surface to respire (breathe).
3. Pupa: The larva develops into a pupa, which also lives in water and comes to the surface for air. Pupae have a comma-like shape.
4. Adult: The pupa transforms into an adult mosquito, which emerges from the water, rests briefly, and then flies away.

The adult mosquito lives for a relatively short time (10-15 days). The female adult mosquito lays eggs, continuing the cycle.

Disrupting the mosquito life cycle, for example, by preventing stagnant water or adding a thin layer of kerosene oil to water surfaces (which prevents larvae and pupae from accessing air), helps control mosquito populations.

Mosquitoes undergo significant changes in appearance and structure (metamorphosis) as they develop from egg to adult.

Extra Information: The silk moth also has a life cycle with egg, larva (silkworm), pupa (cocoon), and adult stages. The silk fibre comes from the material secreted by the larva to form its cocoon around the pupa.

Life Cycle Of A Frog

Frogs are amphibians that also have a life cycle involving transformation.

The life cycle of a frog typically involves four main stages, starting in water:

1. Eggs (Spawn): Frogs lay eggs in clusters, often in shallow water, called spawn. These appear as jelly-like masses.
2. Tadpole: Eggs hatch into larvae called tadpoles. Early tadpoles have a tail and resemble small fish, living entirely in water and breathing with gills. As they grow, hind legs develop, followed by front legs. They still have tails and live in water.
3. Froglet: The tadpole continues to develop, its tail shortens and disappears, and it develops lungs. It becomes a froglet, which starts to resemble a miniature adult frog but may still have remnants of its tail. Froglets begin spending time both in water and on land.
4. Adult Frog: The froglet loses its tail completely, its legs become strong for jumping, and it becomes a fully developed adult frog capable of living on both land and in water.

Frogs undergo significant changes in body shape, structure, and habitat preference throughout their life cycle.

Comparing the life cycles of mosquitoes and frogs shows that both involve metamorphosis (significant changes in form) during development, and both start their lives in water.

All living creatures, both plants and animals, go through life cycles involving growth, development, and reproduction, ensuring the continuation of life on Earth. Understanding these processes helps us appreciate the diversity of life and the importance of conserving habitats.

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer: